---
reviewers:
- janetkuo
title: 基于Replication Controller执行滚动升级
content_template: templates/concept
weight: 80
---
<!-- 
---
reviewers:
- janetkuo
title: Perform Rolling Update Using a Replication Controller
content_template: templates/concept
weight: 80
--- 
-->

## 概述

**注**: 创建副本应用的首选方法是使用[Deployment](/docs/api-reference/{{< param "version" >}}/#deployment-v1beta1-apps)，Deployment使用[ReplicaSet](/docs/api-reference/{{< param "version" >}}/#replicaset-v1beta1-extensions)来进行副本控制。
更多信息, 查看[使用Deployment运行一个无状态应用](/docs/tasks/run-application/run-stateless-application-deployment/)。

<!-- 
{{< note >}}
**Note**: The preferred way to create a replicated application is to use a
[Deployment](/docs/reference/generated/kubernetes-api/{{< param "version" >}}/#deployment-v1-apps),
which in turn uses a
[ReplicaSet](/docs/reference/generated/kubernetes-api/{{< param "version" >}}/#replicaset-v1-apps).
For more information, see
[Running a Stateless Application Using a Deployment](/docs/tasks/run-application/run-stateless-application-deployment/).
{{< /note >}}
-->

为了在更新服务的同时不中断业务， `kubectl` 支持['滚动更新'](/docs/user-guide/kubectl/v1.6/#rolling-update)，它一次更新一个pod，而不是同时停止整个服务。 有关更多信息，请参阅 [滚动更新设计文档](https://git.k8s.io/community/contributors/design-proposals/cli/simple-rolling-update.md) 和 [滚动更新示例](/docs/tasks/run-application/rolling-update-replication-controller/)。
<!-- 
To update a service without an outage, `kubectl` supports what is called [rolling update](/docs/reference/generated/kubectl/kubectl-commands/#rolling-update), which updates one pod at a time, rather than taking down the entire service at the same time. See the [rolling update design document](https://git.k8s.io/community/contributors/design-proposals/cli/simple-rolling-update.md) for more information.
-->

请注意， `kubectl rolling-update` 仅支持Replication Controllers。 但是，如果使用Replication Controllers部署应用，请考虑将其切换到[Deployments](/docs/concepts/workloads/controllers/deployment/). Deployment是一种被推荐使用的更高级别的控制器，它可以对应用进行声明性的自动滚动更新。 如果您仍然希望保留您的Replication Controllers并使用 `kubectl rolling-update`进行滚动更新， 请继续往下阅读：
<!-- 
Note that `kubectl rolling-update` only supports Replication Controllers. However, if you deploy applications with Replication Controllers,
consider switching them to [Deployments](/docs/concepts/workloads/controllers/deployment/). A Deployment is a higher-level controller that automates rolling updates
of applications declaratively, and therefore is recommended. If you still want to keep your Replication Controllers and use `kubectl rolling-update`, keep reading:
-->

滚动更新可以对replication controller所管理的Pod的配置进行变更，变更可以通过一个新的配置文件来进行，或者，如果只更新镜像，则可以直接指定新的容器镜像。
<!--
A rolling update applies changes to the configuration of pods being managed by
a replication controller. The changes can be passed as a new replication
controller configuration file; or, if only updating the image, a new container
image can be specified directly.
-->

滚动更新的工作流程：
<!--
A rolling update works by:
-->

1. 通过新的配置创建一个replication controller
2. 在新的控制器上增加副本数，在旧的上面减少副本数，直到副本数达到期望值
3. 删除之前的replication controller
<!--
1. Creating a new replication controller with the updated configuration.
2. Increasing/decreasing the replica count on the new and old controllers until
   the correct number of replicas is reached.
3. Deleting the original replication controller.
-->

使用`kubectl rolling-update`命令来进行滚动更新：

    $ kubectl rolling-update NAME \
        ([NEW_NAME] --image=IMAGE | -f FILE)
<!--
Rolling updates are initiated with the `kubectl rolling-update` command:

    $ kubectl rolling-update NAME \
        ([NEW_NAME] --image=IMAGE | -f FILE)
-->

## 通过配置文件更新

通过配置文件来进行滚动更新，需要在`kubectl rolling-update`命令后面带上新的配置文件：

    $ kubectl rolling-update NAME -f FILE

这个配置文件必须满足以下条件：

* 指定不同的`metadata.name`值

* 至少要修改`spec.selector`中的一个标签值

* `metadata.namespace`字段必须相同

Replication Controllers的配置文件详细介绍见[创建Replication Controllers](/docs/tutorials/stateless-application/run-stateless-ap-replication-controller/).
<!--
## Passing a configuration file

To initiate a rolling update using a configuration file, pass the new file to
`kubectl rolling-update`:

    $ kubectl rolling-update NAME -f FILE

The configuration file must:

* Specify a different `metadata.name` value.

* Overwrite at least one common label in its `spec.selector` field.

* Use the same `metadata.namespace`.

Replication controller configuration files are described in
[Creating Replication Controllers](/docs/tutorials/stateless-application/run-stateless-ap-replication-controller/).
-->

### 示例

    // 通过新的配置文件frontend-v2.json来更新frontend-v1的pods
    $ kubectl rolling-update frontend-v1 -f frontend-v2.json

    // 将frontend-v2.json数据传到标准输入来更新frontend-v1的pods
    $ cat frontend-v2.json | kubectl rolling-update frontend-v1 -f -
<!--
### Examples

    // Update pods of frontend-v1 using new replication controller data in frontend-v2.json.
    $ kubectl rolling-update frontend-v1 -f frontend-v2.json

    // Update pods of frontend-v1 using JSON data passed into stdin.
    $ cat frontend-v2.json | kubectl rolling-update frontend-v1 -f -
-->

## 更新容器镜像

仅更新容器镜像的话，可通过如下命令，该命令可以指定一个新的控制器名称（可选），通过`--image`参数来指定新的镜像名称和标签。

    $ kubectl rolling-update NAME [NEW_NAME] --image=IMAGE:TAG

`--image`参数仅支持单容器pod，多容器pod使用`--image`参数会返回错误。

如果没有指定 `NEW_NAME` ，新的replication controller创建后会使用一个临时名称，当更新完成，旧的controller被删除后，新的controller名称会被更新成旧的controller名称。

如果`IMAGE:TAG` 和当前值相同，更新就会失败。 因此，我们建议使用版本号来作为标签，而不是使用 `:latest`。从一个 `image:latest`镜像升级到一个新的 `image:latest` 镜像将会失败，即使这两个镜像不是相同的。
所以，我们不建议使用 `:latest` 来作为标签，详细信息见[最佳配置实践](/docs/concepts/configuration/overview/#container-images) 。
<!--
## Updating the container image

To update only the container image, pass a new image name and tag with the
`--image` flag and (optionally) a new controller name:

    $ kubectl rolling-update NAME [NEW_NAME] --image=IMAGE:TAG

The `--image` flag is only supported for single-container pods. Specifying
`--image` with multi-container pods returns an error.

If no `NEW_NAME` is specified, a new replication controller is created with
a temporary name. Once the rollout is complete, the old controller is deleted,
and the new controller is updated to use the original name.

The update will fail if `IMAGE:TAG` is identical to the
current value. For this reason, we recommend the use of versioned tags as
opposed to values such as `:latest`. Doing a rolling update from `image:latest`
to a new `image:latest` will fail, even if the image at that tag has changed.
Moreover, the use of `:latest` is not recommended, see
[Best Practices for Configuration](/docs/concepts/configuration/overview/#container-images) for more information.
-->

### 示例

    // 更新frontend-v1的pod到frontend-v2
    $ kubectl rolling-update frontend-v1 frontend-v2 --image=image:v2

    // 更新frontend的pods，不更改replication controller的名称
    $ kubectl rolling-update frontend --image=image:v2
<!--
### Examples

    // Update the pods of frontend-v1 to frontend-v2
    $ kubectl rolling-update frontend-v1 frontend-v2 --image=image:v2

    // Update the pods of frontend, keeping the replication controller name
    $ kubectl rolling-update frontend --image=image:v2
-->

## 必选和可选字段

必选字段：

* `NAME`: 需要进行滚动更新的replication controller名称

下面两个字段选其一：

* `-f FILE`: 新的replication controller的配置文件，JSON或者YAML格式均可。配置文件必须指定一个新的顶层`id`值，且至少包含一个现有`spec.selector`中的键值对。
  详细信息见[通过Replication Controller运行无状态应用](/docs/tutorials/stateless-application/run-stateless-ap-replication-controller/#replication-controller-configuration-file)。
<br>
<br>
    或者：
<br>
<br>
* `--image IMAGE:TAG`: 更新后的镜像的名称和标签。必须和当前的image:tag不同。

可选字段包括：

* `NEW_NAME`: 只和 `--image` 一起使用，不和 `-f FILE` 一起使用。标识新的replication controller的名称。
* `--poll-interval DURATION`: 在更新后轮询控制器状态的间隔时间。有效单位有 `ns` （纳秒），`us` 或 `µs`（微秒），`ms`（毫秒），`s`（秒），`m`（分钟）或 `h`（小时）。 单位可以自由组合（例如 `1m30s`）。 默认值为 `3s`。
* `--timeout DURATION`: 退出更新之前，等待控制器更新一个pod的最大时间。默认是`5m0s`。有效单位如`--poll-interval`所述。
* `--update-period DURATION`: 更新两个pod之间等待的时间，默认值是`1m0s`。有效单位如`--poll-interval`所述。

有关`kubectl rolling-update`命令的更多信息见[`kubectl`参考](/docs/user-guide/kubectl/v1.6/#rolling-update).
<!--
## Required and optional fields

Required fields are:

* `NAME`: The name of the replication controller to update.

as well as either:

* `-f FILE`: A replication controller configuration file, in either JSON or
  YAML format. The configuration file must specify a new top-level `id` value
  and include at least one of the existing `spec.selector` key:value pairs.
  See the
  [Run Stateless AP Replication Controller](/docs/tutorials/stateless-application/run-stateless-ap-replication-controller/#replication-controller-configuration-file)
  page for details.
<br>
<br>
    or:
<br>
<br>
* `--image IMAGE:TAG`: The name and tag of the image to update to. Must be
  different than the current image:tag currently specified.

Optional fields are:

* `NEW_NAME`: Only used in conjunction with `--image` (not with `-f FILE`). The
  name to assign to the new replication controller.
* `--poll-interval DURATION`: The time between polling the controller status
  after update. Valid units are `ns` (nanoseconds), `us` or `µs` (microseconds),
  `ms` (milliseconds), `s` (seconds), `m` (minutes), or `h` (hours). Units can
  be combined (e.g. `1m30s`). The default is `3s`.
* `--timeout DURATION`: The maximum time to wait for the controller to update a
  pod before exiting. Default is `5m0s`. Valid units are as described for
  `--poll-interval` above.
* `--update-period DURATION`: The time to wait between updating pods. Default
  is `1m0s`. Valid units are as described for `--poll-interval` above.

Additional information about the `kubectl rolling-update` command is available
from the [`kubectl` reference](/docs/reference/generated/kubectl/kubectl-commands/#rolling-update).
-->

## 实践

现在你运行了一个1.7.9版本的nginx应用：

```yaml
apiVersion: v1
kind: ReplicationController
metadata:
  name: my-nginx
spec:
  replicas: 5
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx:1.7.9
        ports:
        - containerPort: 80
```

要更新到1.9.1版本，你可以使用[`kubectl rolling-update --image`](https://git.k8s.io/community/contributors/design-proposals/cli/simple-rolling-update.md)来指定一个新的镜像：

```shell
$ kubectl rolling-update my-nginx --image=nginx:1.9.1
Created my-nginx-ccba8fbd8cc8160970f63f9a2696fc46
```

在终端上打开另一个窗口 ，你可以看到`kubectl` 给每个pod都增加了一个值为配置文件哈希值的 `deployment` 标签，用来区分新旧pod：

```shell
$ kubectl get pods -l app=nginx -L deployment
NAME                                              READY     STATUS    RESTARTS   AGE       DEPLOYMENT
my-nginx-ccba8fbd8cc8160970f63f9a2696fc46-k156z   1/1       Running   0          1m        ccba8fbd8cc8160970f63f9a2696fc46
my-nginx-ccba8fbd8cc8160970f63f9a2696fc46-v95yh   1/1       Running   0          35s       ccba8fbd8cc8160970f63f9a2696fc46
my-nginx-divi2                                    1/1       Running   0          2h        2d1d7a8f682934a254002b56404b813e
my-nginx-o0ef1                                    1/1       Running   0          2h        2d1d7a8f682934a254002b56404b813e
my-nginx-q6all                                    1/1       Running   0          8m        2d1d7a8f682934a254002b56404b813e
```

使用`kubectl rolling-update`可以实时看到更新的进度： 

```
Scaling up my-nginx-ccba8fbd8cc8160970f63f9a2696fc46 from 0 to 3, scaling down my-nginx from 3 to 0 (keep 3 pods available, don't exceed 4 pods)
Scaling my-nginx-ccba8fbd8cc8160970f63f9a2696fc46 up to 1
Scaling my-nginx down to 2
Scaling my-nginx-ccba8fbd8cc8160970f63f9a2696fc46 up to 2
Scaling my-nginx down to 1
Scaling my-nginx-ccba8fbd8cc8160970f63f9a2696fc46 up to 3
Scaling my-nginx down to 0
Update succeeded. Deleting old controller: my-nginx
Renaming my-nginx-ccba8fbd8cc8160970f63f9a2696fc46 to my-nginx
replicationcontroller "my-nginx" rolling updated
```

如果遇到问题，你可以中途停止滚动更新，并且使用 `--rollback` 来回滚到以前的版本:

```shell
$ kubectl rolling-update my-nginx --rollback
Setting "my-nginx" replicas to 1
Continuing update with existing controller my-nginx.
Scaling up nginx from 1 to 1, scaling down my-nginx-ccba8fbd8cc8160970f63f9a2696fc46 from 1 to 0 (keep 1 pods available, don't exceed 2 pods)
Scaling my-nginx-ccba8fbd8cc8160970f63f9a2696fc46 down to 0
Update succeeded. Deleting my-nginx-ccba8fbd8cc8160970f63f9a2696fc46
replicationcontroller "my-nginx" rolling updated
```

这个例子说明容器的不变性是个巨大的优点。

如果你不仅仅是需要更新镜像，(例如，更新命令参数，环境变量等)，你可以创建一个新的replication controller配置文件，包含一个新的名称和不同的标签值，例如：

```yaml
apiVersion: v1
kind: ReplicationController
metadata:
  name: my-nginx-v4
spec:
  replicas: 5
  selector:
    app: nginx
    deployment: v4
  template:
    metadata:
      labels:
        app: nginx
        deployment: v4
    spec:
      containers:
      - name: nginx
        image: nginx:1.9.2
        args: ["nginx", "-T"]
        ports:
        - containerPort: 80
```

然后使用它来进行更新：

```shell
$ kubectl rolling-update my-nginx -f ./nginx-rc.yaml
Created my-nginx-v4
Scaling up my-nginx-v4 from 0 to 5, scaling down my-nginx from 4 to 0 (keep 4 pods available, don't exceed 5 pods)
Scaling my-nginx-v4 up to 1
Scaling my-nginx down to 3
Scaling my-nginx-v4 up to 2
Scaling my-nginx down to 2
Scaling my-nginx-v4 up to 3
Scaling my-nginx down to 1
Scaling my-nginx-v4 up to 4
Scaling my-nginx down to 0
Scaling my-nginx-v4 up to 5
Update succeeded. Deleting old controller: my-nginx
replicationcontroller "my-nginx-v4" rolling updated
```
<!--
## Walkthrough

Let's say you were running version 1.7.9 of nginx:

```yaml
apiVersion: v1
kind: ReplicationController
metadata:
  name: my-nginx
spec:
  replicas: 5
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx:1.7.9
        ports:
        - containerPort: 80
```

To update to version 1.9.1, you can use [`kubectl rolling-update --image`](https://git.k8s.io/community/contributors/design-proposals/cli/simple-rolling-update.md) to specify the new image:

```shell
$ kubectl rolling-update my-nginx --image=nginx:1.9.1
Created my-nginx-ccba8fbd8cc8160970f63f9a2696fc46
```

In another window, you can see that `kubectl` added a `deployment` label to the pods, whose value is a hash of the configuration, to distinguish the new pods from the old:

```shell
$ kubectl get pods -l app=nginx -L deployment
NAME                                              READY     STATUS    RESTARTS   AGE       DEPLOYMENT
my-nginx-ccba8fbd8cc8160970f63f9a2696fc46-k156z   1/1       Running   0          1m        ccba8fbd8cc8160970f63f9a2696fc46
my-nginx-ccba8fbd8cc8160970f63f9a2696fc46-v95yh   1/1       Running   0          35s       ccba8fbd8cc8160970f63f9a2696fc46
my-nginx-divi2                                    1/1       Running   0          2h        2d1d7a8f682934a254002b56404b813e
my-nginx-o0ef1                                    1/1       Running   0          2h        2d1d7a8f682934a254002b56404b813e
my-nginx-q6all                                    1/1       Running   0          8m        2d1d7a8f682934a254002b56404b813e
```

`kubectl rolling-update` reports progress as it progresses:

```
Scaling up my-nginx-ccba8fbd8cc8160970f63f9a2696fc46 from 0 to 3, scaling down my-nginx from 3 to 0 (keep 3 pods available, don't exceed 4 pods)
Scaling my-nginx-ccba8fbd8cc8160970f63f9a2696fc46 up to 1
Scaling my-nginx down to 2
Scaling my-nginx-ccba8fbd8cc8160970f63f9a2696fc46 up to 2
Scaling my-nginx down to 1
Scaling my-nginx-ccba8fbd8cc8160970f63f9a2696fc46 up to 3
Scaling my-nginx down to 0
Update succeeded. Deleting old controller: my-nginx
Renaming my-nginx-ccba8fbd8cc8160970f63f9a2696fc46 to my-nginx
replicationcontroller "my-nginx" rolling updated
```

If you encounter a problem, you can stop the rolling update midway and revert to the previous version using `--rollback`:

```shell
$ kubectl rolling-update my-nginx --rollback
Setting "my-nginx" replicas to 1
Continuing update with existing controller my-nginx.
Scaling up nginx from 1 to 1, scaling down my-nginx-ccba8fbd8cc8160970f63f9a2696fc46 from 1 to 0 (keep 1 pods available, don't exceed 2 pods)
Scaling my-nginx-ccba8fbd8cc8160970f63f9a2696fc46 down to 0
Update succeeded. Deleting my-nginx-ccba8fbd8cc8160970f63f9a2696fc46
replicationcontroller "my-nginx" rolling updated
```

This is one example where the immutability of containers is a huge asset.

If you need to update more than just the image (e.g., command arguments, environment variables), you can create a new replication controller, with a new name and distinguishing label value, such as:

```yaml
apiVersion: v1
kind: ReplicationController
metadata:
  name: my-nginx-v4
spec:
  replicas: 5
  selector:
    app: nginx
    deployment: v4
  template:
    metadata:
      labels:
        app: nginx
        deployment: v4
    spec:
      containers:
      - name: nginx
        image: nginx:1.9.2
        args: ["nginx", "-T"]
        ports:
        - containerPort: 80
```

and roll it out:

```shell
$ kubectl rolling-update my-nginx -f ./nginx-rc.yaml
Created my-nginx-v4
Scaling up my-nginx-v4 from 0 to 5, scaling down my-nginx from 4 to 0 (keep 4 pods available, don't exceed 5 pods)
Scaling my-nginx-v4 up to 1
Scaling my-nginx down to 3
Scaling my-nginx-v4 up to 2
Scaling my-nginx down to 2
Scaling my-nginx-v4 up to 3
Scaling my-nginx down to 1
Scaling my-nginx-v4 up to 4
Scaling my-nginx down to 0
Scaling my-nginx-v4 up to 5
Update succeeded. Deleting old controller: my-nginx
replicationcontroller "my-nginx-v4" rolling updated
```
-->

## 故障分析

如果更新过程中，达到超时时长`timeout`后还没更新完成，则更新会失败。这时，一些pod会属于新的replication controller，一些会属于旧的。

如果更新失败，可以尝试使用同样的命令来继续更新过程。

在尝试更新之前如果需要回滚到之前的状态，可在之前的命令后面添加`--rollback=true`参数，这将回退所有的更改。
<!--
## Troubleshooting

If the `timeout` duration is reached during a rolling update, the operation will
fail with some pods belonging to the new replication controller, and some to the
original controller.

To continue the update from where it failed, retry using the same command.

To roll back to the original state before the attempted update, append the
`--rollback=true` flag to the original command. This will revert all changes.
-->
